Introduction to physics

WHAT IS PHYSICS?

From Greek word ‘physikos’

IS A BRANCH OF SCIENCE CONCERNING THE STUDY ABOUT NATURAL

PHENOMENA AND PROPERTIES OF MATTER

HAVE YOU EVER WONDER?

Why hot coffee will gradually turn cold

after an hour?

How your image can be formed on

mirror?

Forces and

pressure

Electric and

Electronic

Wave

Electromagnetism

Physical quantityIs a quantity that can be measuredEg: mass, length, volume, temperature

Base quantity Derived quantity

Is a quantity that cannot be derived in other base quantity.

Is a quantity that can be derived from other base quantity by multiplication or division.

Base Quantity SI unitsLength, l metres, mMass, m kilogram,

kg

Time, t second, sTemperature, T Kelvin, k Electrical current, I Ampere, A

Derived Quantity Units

Volume, V m3

Density, kgm-3

Velocity, v ms-1

Force, F N

Acceleration, a ms-2

Base quantity Derived quantity

Prefixes Use to represent physical quantities which

are very big or very small in S.I units.Prefix Symb

olMultiplication

factorValue

Tera T × 1012 1 000 000 000 000

Giga G × 109 1 000 000 000Mega M × 106 1 000 000Kilo k × 103 1000Deci d × 10-1 0.1Centi c × 10-2 0.01Milli m × 10-3 0.001Micro × 10-6 0.000001Nano n × 10-9 0.000000001Pico p × 10-12 0.000000000001

Scientific notation/ Standard form

Numerical values which very small or big can be written in standard form:

A × 10n

(1 ≤ A < 10, positive or negative integer)Exercises:1)Write 0.0000008 in scientific notation.2)The equatorial diameter of earth is 12 760

000 m. Write the diameter in standard form.

Conversion unitConvert the measurement:a)5.7 cm to metre

b)1.5 km to metre

c)1.1 g cm-3 to kg m-3

d)1.45 × 10-2 Mm to m

e)2.25 × 1010 μm to m

f)2.2 × 108 Gm to m

g)36 kmh-1 to ms-1

h)8 cm2 to km2

i) 16 m2 to cm2

j) 8.1 kgm-3 to gcm-3

k)25 ms-1 to kmh-1

1.3.1 Measure physical quantity using appropriate instruments.

a) Metre rule

Function Sensitivity

Measure length from a few cm up to 1m

0.1 cm

b) Thermometer

Function Sensitivity

Measure temperature. 1oC / 2oC

c) Stopwatch

Function Sensitivity

Measure time intervals. 0.1 s to 0.2 s

d) Ammeter

Function Sensitivity

Measure electric current. 0.1 A / 0.2 A

e) Voltmeter

Function Sensitivity

Measure potential difference / voltage.

0.1 V / 0.2 V

f)Measuring tape

Function Sensitivity

Measure long distance, circumference of round

object.

1.0 cm

g) Vernier callipers

Function Sensitivity

Measure length, diameter inner and outer and depth object with dimension up

to 12.0 cm.

0.01 cm

Function

Main scale Scale of 0.1 cm to 12 cm

Inside jaws Measure internal diameter

Outside jaws Measure external diameter and length

Tail Measure depth

How to take reading of vernier callipers?1. Read main scale reading Observe the zero mark ‘0’ on vernier scale. The vernier scale lies between 1.2 cm and 1.3 cm. Reading on main scale is 1.2 cm.2. Read vernier scale reading Read mark on vernier scale that is exactly in line

with any mark on main scale. Reading on vernier scale= 0.03 cm

Reading = Reading on + Reading on main scale vernier scale

= 1.2 + 0.03 cm = 1.23 cm

Main scale

Vernier scale

h) Micrometer Screw Gauge

Function Sensitivity

Measure thickness or diameter of small object in range between 0.10 mm

and 25.00 mm.

0.01 mm or 0.001 cm

Function

Anvil and spindle Used to grip object.

Sleeve Main scale

Thimble Thimble scale

Ratchet knob Used to prevent exceeding pressure

1. Read main scale reading Read main scale at edge of thimble Reading main scale = 5.5 mm2. Read thimble scale reading Thimble scale reading = 0.28 mm

How to take reading of micrometer screw gauge?

Reading = Main scale + Thimble scale

= 5.5 + 0.28 = 5.78 mm

The smaller the change which can be measured by instrument, the more sensitive the instrument is.

The smallest scale division on measuring instruments is the more sensitive the instrument is.

Different measuring instruments have different levels of sensitivity.

1.3.2 Explain SensitivitySensitivity of an instruments is its

ability to detect small change in the quantity to be measured.

Which one is more sensitive?

1.3.2 Explain Accuracy and Consistency

ACCURACY CONSISTENCY

Is how close the value of the measurement to the actual value.

Ability to register the same reading.

Consistence Inconsistence

Accurate

Inaccurate

ACCURACY CONSISTENCYHow to improve accuracy:1.Repeat the experiment and take average reading.2.Avoid zero error.3.Avoid parallax error.4.Use measuring instrument with high sensitivity.

How to improve consistency:1.Avoid parallax error.

Consistence but not accurate

Accurate but inconsistence

Inaccurate and Inconsistence

Accurate and consistence

SYSTEMATIC ERROR RANDOM ERROR

1. Zero error Incorrect position of zero

point of measuring instrument.

2. Incorrect calibration Error in calibration of

instrument which makes the instrument defective.

- Systematic error will lead to decrease in accuracy.

1. Parallax error error because of the

observers eyes.2. Natural error change in temperature,

humidity etc when experiment in progress

3. Wrong technique apply excessive pressure.

- Random error will lead to decrease in consistency.

How to reduce systematic error:Correct reading = reading obtained - zero error

How to reduce random error: Repeat the experiment and take average reading.

1.3.3 Explain Types of Experimental Error

Zero error

Parallax error

How to eliminate zero error?

Micrometer Screw Gauge

Negative zero error

Zero error= -0.04 mm

Positive zero error

Zero error= 0.02 mm

Vernier Callipers

No zero error

Negative zero error

Positive zero error

zero error = 0.04 cm

zero error = -0.02 cm